As I have said before many times, the different programs get the same results with no significant differences if they are set up correctly and if the file is not a dodgy one. There are sometimes files with errors and sometimes those errors are quite large. The different programs sometimes handle those errors differently and come up with a different result, but usually it is fairly obvious there is an error in the stand alone programs. When these errors are discovered and reported, the authors of the various programs work hard to find a solution so they handle then with the same result, usually rejection. Dylan is no exception, but when those errors pop up in KA72, they may not be picked up unless they are quite obvious and/or have been checked in one or more of the other programs. Just because any program gives you a peak speed PB 5 knots higher than you have ever approached before, does not mean it is necessarily true! You could just have discovered yet another way to screw up the program calculations, and in spite of constant troubleshooting and problem solving to try to cover every possible error situation, it amazes me that we are constantly finding more ways to screw up the calculations. Most of the recent issues have involved new GPS units like the 5hz GW-52 or the 10hz Thingsee One that present new challenges for the software designers, GPS units that save limited data like the Canmore, or GPS users that find ever more ways to disrupt or interfere with the GPS signal to their GPS antenna.
In the days before KA72 when everyone had to analyse their own data in a program on their own computer, most users quickly got a feel for what looked right and what didn't. If they were not sure they would usually ask someone else to check it. But still, some errors did get through.
What I am trying to impart here is that you can not always trust computer software to give you a valid result in every conceivable situation. You need to be aware of things that sound a bit too good (or bad) to be true. Its not unlike the kids in math class who punch some numbers into a calculator and come up with a figure they just accept without looking to see if it actually makes sense. (That is one of the big challenges of Math teachers today).
For example, when my good friend, and super fast sailor Jaques had a 50 knot peak speed on one of his two GT-31 GPS's we were all pretty stoked for him. Then we noticed his other GPS only had a high 48 peak. Although we really, really wanted the 50 to be true, further investigation clearly revealed it to be an error. Very disappointing to say the least.
If he had only used one GPS, it would have been very much more difficult to spot the error, and even harder to accept the analysis that it was an error.
I could give you dozens of examples, but you have probably seen or heard of a few yourself.
So here is another example. I picked a random file from my recent sessions and ran it in RealSpeed v1.929, GPSAR-Pro v5.4, GPS-Results V6.144 and KA-72 Speed Reader.
Now before someone jumps up and down and tells me 'see, they are different'........
Some of the differences are due to rounding of the third decimal point. Totally insignificant!!
GPSAR-Pro refused to give me an Alpha result. This is because the results from the other programs are of a very unusual Alpha where I actually stopped and set off again. Not really a proper Alpha and one could argue that only GPSAR-Pro got it right in this case. But is also remarkable that all the other programs got exactly the same result from what is clearly a dodgy Alpha. When I have run proper Alphas in various programs with clean files I have always get EXACTLY the same results.
The 1hr Results are slightly different and I can't explain that except to observe that they are two and two. There must be a slightly different parameter in the calc somewhere and it was good I found it here. Yet another like of investigation opens. But again, the difference of 0.18 knots is hardly going to be significant in any competition and would mostly be smaller than the maximum error deviation (SDOP).
The total distances is an interesting one because this is where the program defaults may need to be tweaked by the user.
GPS-Results come with a min speed of 5 knots set as default. The policy of GPS-TC and WGPSSRC is to set it at zero and accept small incidental distances of drifting or walking to the waters edge and back etc. If you have GPS-Results, set it to zero and turn off 'filters' and you should get identical results to RealSpeed.
GPSAR-Pro also allows setting of a min speed. I don't what the default setting is but mine was set to zero. It still got a slightly different result but it was the same as KA72. Yet another line of investigation appears. I will need to check if this is consistent over various files. In any case, the difference of a few tenths of a KM is not significant.
So there you have it. I stress that I just picked on file at random. I didn't run a few and cherry pick one to enhance the comparison as is clearly evident.
I think any reasonable person would agree with me that all the programs give the same results from a clean file.
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